Engines utilize various types of fuel injection adjustments to provide improved engine performance. One example fuel injection compensation methods increases or decreases fuel injection to account for fuel adhered to walls of the intake manifold, intake valves, and/or intake ports. Such phenomena may be referred to as wall wetting dynamics, or transient fuel dynamics. To compensate for such dynamics, the amount of fuel injected is varied to compensate for the fuel stored in the intake manifold and intake ports based on various models and estimates taking into account engine operating conditions. In this way, more accurate air/fuel ratio control may be achieved in of the combusted air/fuel mixture.
One example of fuel injection control is described in U.S. Pat. No. 5,492,101. In this example, a transient fuel compensation is described that uses an atomized fuel behavioral model, intake passage fuel behavioral model, and a combustion fuel behavioral model to adjust fuel injection and control actual air/fuel ratio in the combustion chamber. Specifically, the approach utilizes a fuel property value (NF) in the intake passage behavioral model.
The inventors herein have recognized several issues with the above approach. First, there may be numerous fuel properties that may be included in the model, some of which may have an influence of increasing fuel injection compensation while others have an influence of decreasing fuel injection compensation. Second, the inventors herein have also recognized that the determination of fuel properties may require additional sensors, thus increasing costs.
In one embodiment, the above issues may be addressed by utilizing fuel volatility to adjust transient fuel injection, where the fuel volatility is determined during previous engine start-up operation. For example, Applicants have recognized that fuel volatility and/or quality can have an impact on air-fuel control during transient fueling conditions by affecting the amount of fuel stored in the intake manifold and ports, the rate of storage, and/or the rate of release. Further, by determining fuel volatility during a start, it is possible to determine an indication of fuel volatility by monitoring engine run-up speed.